It could be any of the above ... your best bet is to test each component individually.

For testing the RAM I suggest a bootable cd with memtest86+ on it (Ubuntu instalation disk has it, also Hiren CD has memtest on it). Let it perform at least 3 passes.

For testing the video, download ATITool and let is find artifacts for a half an hour. This tool also works on nVidia cards.

To see if the computer overheats, after a blue screen or reboot, check the BIOS and see the overall temperature and/or CPU temperature. If it's almost at the limit it might be overheating. Try reproducing the blue screen while leaving your computer case open and using a normal fan to keep a steady airflow on the components. If while you're doing this the computer is ok, you might want to buy an extra fan or two for your case.

For mobo Hiren Boot CD also has a few tests on it but I can't recommend any since I haven't used them

You must run memtest86+ it's the best ram test you'll ever find. Also if you have some fancy DDR3 memory kit, make sure you have them plug in the correct slots on the mobo (you should find some specs in the manual regarding the triple channel setup and all that).

Also when testing the ram, you must do several test. 1. Test the memory modules they way they are set up now. 2. In case you get errors and you have more than 1 module, test each module alone on all the slots.

If one module gives error on more than one slot it's the module. If both modules give errors on the same slot, that memory slot on the mobo might be the problem.

Also (with the risk of Gizmo editing my post but hopefully since I'm part of the somewhat active members here, he won't :D) why would you pay for Windows 7? Just download it.

Im having trouble making a disc image file dvd. The nero software im using is new enough to handle it but it can't find the correct supported files in the locations I am sure the memtest and win7 .iso files are in.